The above identified copending application is directed toward a finger actuated pump dispenser for pharmaceutical applications which not only discharges fluid at a predetermined pressure but also delivers a predetermined dosage regardless of the method of actuation employed. However, when the dispenser is actuated after it has been stored unused for some period, fluid will have evaporated from the volume within the actuator and the fluid pathway between the chamber seal and the finger controlled actuator. Consequently, the dose delivered by the first actuation will be somewhat less then delivered by subsequent actuations. In some pharmaceutical applications, it is essential for the dispenser to deliver an accurate dose upon such first actuation. The present invention eliminates this evaporation and thus insures accurate dose delivery at all times.